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Re: HDTV WHY???
- To: telecine at sun.alegria.com
- Subject: Re: HDTV WHY???
- From: Tom McMahon <tlm at microsoft.com>
- Date: Sun, 28 Sep 1997 04:58:23 -0700 (PDT)
- Old-Date: Sun, 28 Sep 1997 04:58:00 -0700
- Old-Return-Path: <rob>
- Organization: Altruistic Intentions, Hollywood, CA
- Phone-number: +1 213 464 6266
- Reply-To: Rob Lingelbach <rob at alegria.com>
- Resent-Date: Sun, 28 Sep 1997 07:42:34 -0700
- Resent-From: rob at sun.alegria.com (Rob Lingelbach)
- Resent-Message-Id: <m0xFKYM-0007lYC at sun.alegria.com>
- Resent-Sender: telecine-request at sun.alegria.com
- Resent-To: telecine internet group <telecine at alegria.com>
> unknown new format will probably be chosen by the consumer in the
> 3. More than likely, this unknown new consumer HDTV recording
> format will
> have to be progressive scan at base-band.
The transmitted digital television "signal" in both the ATSC and DVB
systems is a compressed MPEG-2 bitstream. There will be real time
high quality MPEG-2 decoders in most DTV receivers, whether they be
HDTV, (H)DTV, hDTV or just DTV. (Depends on your definition of High
Definition). These decoders will unravel that compressed signal and
cause it to be splashed up on any one of a number of different screen
sizes and display technologies starting next year, whether those
displays be progressive or interlaced. However, you won't have to
decompress the signal and turn it into baseband video in order to
record it. (Actually, some DTV receivers may not even have a display.
They'll simply pick up the broadcast signal and peel off any data that
happens to be attached to it, discarding the video completely.)
Consumer electronics manufacturers will be offering what amount to
cheap data-recorders (sometimes built on VHS substrate technologies).
These devices will allow one to record the compressed bitstream
(around 18-22 Mbits/sec) off of any particular broadcast channel,
including pre-programmed time slots (just like your VCR) for time
shifting and other consumer applications.
This compressed stream is actually the highest possible quality form
of the DTV transmission; its reproduction will depend solely on the
receiver or display device you wish to play it back on, not the
bandwidth or sampling structure of the recording system. These
data-recorders have an added advantage in that they'll also record any
ancillary data "enhancements" that may have been shipped along with
that digital program stream. (Not to mention also recording the 5.1
Channel AC-3 or MPEG-2 audio content.)
Note that computer-based DTV receiving appliances can simply record
the compressed digital bitstream to their hard drive where it can be
dealt with later.
> 5. Most consumers not in our industry still mistake 525/625
> component images viewed on a standard component monitor as being
Not bad stuff, done right!
> I am willing to bet that the majority of consumers will see
> (practically?) no difference between 525/626 16:9 component
> digital images
> sampled at 18mhz. vs. those at 1920x1080i.
Agreed. This holds true on most consumer-type screen sizes up to and
including 36 inches, especially if the source was film-originated.
These DTV transmissions will have no ghosts, no snow, are 16:9/wide
and will be equipped with very high quality digital audio. Studies
have shown that those attributes coupled with good brightness and
contrast are the biggest win for consumers, not to mention the other
interactive services that will be coming along in the near future.
Actually, in recent tests of the four most likely formats to be used
in North America (480 interlaced, 480 progressive, 720 progressive,
and 1080 interlaced), the Most Significant Bit (MSB) was going from
480I to 480P. Simply getting rid of the interlace caused the biggest
perceptible increase in quality given a constant screen size. 720P
was a bit better in sharpness, granted, but more cost. 1080I was a
mixed bag of somewhat increased sharpness on some scenes but a return
to interlace artifacts on others. Bang for the buck at several screen
heights of viewing distance puts 480P dead on the sweet spot in terms
of best consumer viewing experience at a high level of
> Time-Warner) that mandates all their film transfers be done in
> 1920x1080i. This is unfortunate because it jumps the gun an
> amortizing any reasonable approach to other more useful formats. Oh
> well, that's good for Phillips telecine sales, I guess.
DTV film footage won't commonly be Telecine'd from the film domain to
the electronic domain directly at final resolution (from which it will
be compressed and then transmitted). It will arrive at the final
transmitted format after a series of post production and processing
The initial scanning operation will be performed in one of two ways:
1) Scan into the "data" domain with one of the high resolution
digitizing technologies such as the Philips' Datacine, Cintel, or
Kodak products (or perhaps those world-class devices at Pacific
Title...), using large high bandwidth servers such as SGI for storage
and processing, or: 2) Telecine to 1080/30I video tape (currently
1035/30I) with a 3:2 pulldown inherent in it, as is done by Sony HD
and a number of other places these days. Note that this 1080/30I is
really 1080/24 progressive on the inside...
In this second scenario, "1080/30I" will be used simply as a
production medium, with redundant field information padded for
simplicity and ease in recording and post production using relatively
standard video equipment from vendors such as Sony and Panasonic.
Careful facilities design and operator discipline in keeping track of
the 3:2 sequence during post (scratch removal, color correction, pan
and scan, compositing, titling, etc) keeps the 3:2 sequence sacred so
it can be removed prior to the eventual format conversion and
compression without side effects.
Production in 1920 by 1080 by 24P or, as in number 1 above (high
resolution "data" domain), actually has many advantages due to the
higher spatial (and sometimes chroma and dynamic range) resolution .
The impact of generation loss in post production (yes, even in the
component digital domain) is lessened. The resulting product after a
format conversion and subsequent
compression/transmission/decode/display cycle is superior.
There are a growing number of facilities that operate in these modes
today - where they use 2K progressive data or "thousand line
progressive video" as an electronic intermediate format to keep the
highest possible resolution, while maintaining all of the benefits of
interactive electronic processing, until the final mastering steps and
archiving, customer distribution, format conversion and transmission.
Sometimes format conversion will occur just prior to delivery to the
broadcaster. Sometimes it will occur after, upon receipt, for a
further value-add or editing prior to transmission. This is simply a
contractual matter that has nothing whatsoever to do with the HDTV
politics or government mandates.
Furthermore, and just as important, these enlightened modes of
operation completely decouple the origination and post production
formats from the distribution and eventual transmission formats. The
formats used in each part of the foodchain are necessarily different
today. This will probably always be the case, perhaps even more so as
we enter the DTV age.
Hollywood's infrastructure changes at its own pace. The economic
models are different at each pipe stage. Production, Post and
Broadcast facilities are commonly not co-sited. Re-purposing of
content is rampant. DVDs are coming to bear. There are also
international distribution and format or standards issues. Internet
broadcasts are looming. Decoupling makes business sense.
DelRey Graphics, Playa Del Rey, CA
Thanks to Michael Mazur for support of the TIG
TIG subscriber count is 853 on Sun Sep 28 07:42:37 PDT 1997
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